Rich in regrets, this astute 1989 compilation of never-produced songs by Richard Maltby Jr. and David Shire (creators of Baby) offers a slew of bittersweet ballads for nonlovers, antilovers, and mature lovers. Nick Bowling’s staging for Porchlight Music Theatre Chicago features five superb performers (a number that allows for the strategic odd person out) who turn the 24 songs into 24 scenes, each with its own climax, cleverly detailing fading friendships, second chances, sexual survival, unrequited everything, and the march of time and those it tramples. As the pseudo-Sondheim opener, “Doors,” and Kevin Hagan’s multiportal set suggest, for every amorous setback there’s an equally unsought prospect. Perhaps these fortunate falls account for the resilience in, say, Rob Lindley’s rendition of a heartfelt salute to going love-crazy on a roof. We should all be as miserably happy as this high-energy tribute to tribulation. Through 3/13: Fri-Sat 8 PM, Sun 3 PM. Theatre Building Chicago, 1225 W. Belmont, 773-327-5252. $27-$30.